This invention relates generally to communications networks and, more particularly, to synchronous digital interfaces for connecting communications components in communications networks.
A communications system may be created by connecting various communication components such as servers, timeswitches, hubs, and data processing modules. Multiple communications systems connected together form a communications network. Many communications systems include a media services card (MSC); a personal computer (PC) card that performs call processing and media processing of voice channels in the network. The MSC can also be the central interconnect location of a communications network. It accomplishes this task by handling time switching of synchronous channels and interworking with other components in the communications network.
FIG. 1 shows a conventional communications network with a MSC 20 connected to a server 10, and shows the MSC connected to other communications equipment via a synchronous interface 40. A MSC can also include a hub 50, timeswitch 60, media service component 70, and other modules 30. In addition, a MSC can be connected to central units, such as servers 10, via a slot in a PC (e.g. Peripheral Component Interconnect standard (PCI 2.1) slot). This allows interfacing with the server processor and other peripherals used in a communication system. Data packets may be transmitted between the MSC 20 and the server 10, other internal modules 30, or external modules and systems, thereby creating the communications network.
FIG. 1 also shows the MSC card connected to an expansion chassis 80 via an interconnection 40. The interconnections between them can be used for trunk and line connections. Trunk and line interfaces provide access to telecommunications trunks and station set lines. Trunk and station set lines can include Caller ID Analog Trunk interfaces, T1/E1/PRI trunk with channel service unit interfaces, and Analog and Digital phone interfaces. These interfaces are the conduits that pass information throughout the network.
FIG. 2 shows a communications network architecture (with the servers not shown). The network is physically arranged as a branched tree, with a timeswitch 200 at the root and modules 210 as the end nodes. Intermediate nodes are called hubs 220. This physical arrangement allows for point-to-point links at all interfaces. The systems and methods of interfacing between the devices are important components of communications systems and networks. As systems and networks grow, the interfaces handle greater amounts of data and connect to more devices. Present interfaces, however, are substantially limited in channel capacity, expansion capabilities, and the like.
There are many electrical synchronous interfaces available, however, these existing electrical synchronous interfaces are slow and limited in capacity. Those that are expandable are expensive, impractical (e.g. must cascade multiple interface cards), suffer from speed limitations, are electrically noisy, prone to interference from outside sources, and lack features such as maintenance signaling and automatic propagation delay calibration and compensation. Fiber-optic interfaces have been used as synchronous digital interfaces. However, fiber-optic interfaces are more expensive to implement and are much less common than electrical interfaces.
Accordingly there exists a need for systems and methods of synchronous digital interfacing that efficiently use existing wiring schemes.
There also exists a need for systems and methods of synchronous digital interfacing that do not require a clock source or sensitive clock recovery circuit in the peripherals in order to use the interface.
There also exists a need for systems and methods of synchronous digital interfacing that efficiently support multiple peripheral devices.
There also exists a need for systems and methods of synchronous digital interfacing that improve immunity to radio frequency interference (RFI).
There also exists a need for systems and methods of synchronous digital interfacing that reduce RF emissions.
There also exists a need for systems and methods of synchronous digital interfacing that allow for network synchronization control in the peripherals.
There also exists a need for systems and methods of synchronous digital interfacing that support automatic configuration.
There also exists a need for systems and methods of synchronous digital interfacing that support multiple cable lengths.
There also exists a need for systems and methods of synchronous digital interfacing that allow for insertion and removal of powered peripheral devices onto the network without disrupting the network.
There also exists a need for systems and methods of synchronous digital interfacing that interwork with an existing flow-controlled message transport without using any dedicated signaling bandwidth.
Accordingly, it is an object of the present invention to provide systems and methods of synchronous digital interfacing that efficiently uses existing wiring schemes.
It is also an object of the present invention to provide of synchronous digital interfacing that do not require a clock source or sensitive clock recovery circuit in the peripherals in order to use the interface.
It is also an object of the present invention to provide systems and methods of synchronous digital interfacing that efficiently support multiple peripheral devices.
It is also an object of the present invention to provide systems and methods of synchronous digital interfacing that improve immunity to RFI.
It is also an object of the present invention to provide systems and methods of synchronous digital interfacing that reduce RF emissions.
It is also an object of the present invention to provide systems and methods of synchronous digital interfacing that allow for network synchronization control in the peripherals.
It is also an object of the present invention to provide systems and methods of synchronous digital interfacing that support automatic configuration.
It is also an object of the present invention to provide systems and methods of synchronous digital interfacing that are usable with different cable types.
It is also an object of the present invention to provide systems and methods of synchronous digital interfacing that support multiple cable lengths.
It is also an object of the present invention to provide systems and methods of synchronous digital interfacing that allow for insertion and removal of powered peripheral devices without disrupting a network.
It is also an object of the present invention to provide systems and methods of synchronous digital interfacing that interwork with an existing flow-controlled message transport without using any dedicated signaling bandwidth.
These and other objects of the invention will become apparent to those skilled in the art from the following description thereof.
In accordance with the teachings of the present invention, these and other objects may be accomplished by the present invention, which is a synchronous digital interface for connecting components in a communications network.
An embodiment of the invention includes a device configured to transmit and receive differential signals. One set of the differential signals includes a transmit signal and a receive signal. A second set of the differential signals includes a clock signal and a synchronization signal. Combinations of the clock signal and the synchronization signal form other signals having variable periods. The other signals can be used to modify the first set of differential signals.
Another embodiment of the present invention includes a method of synchronously digitally interfacing components in a communications network. This embodiment involves transmitting and receiving differential signals. A first set of differential signals includes a transmit signal and a receive signal. A second set of differential signals includes a clock signal and a synchronization signal. This embodiment also includes forming other signals having variable periods by combining the clock signal and the synchronization signal. This embodiment further includes modifying the first set of differential signals using the other signals.
Another embodiment of the present invention includes a transmission module for transmitting and receiving differential signals. A first set of differential signal includes a transmit signal and a receive signal. A second set of differential signals includes a clock signal and a synchronization signal. It includes a module for combining the clock signal and the synchronization signal to form other signals having variable periods. The other signals are used to modify the first set of differential signals.